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Journal ArticleDOI

Formation of hexagonal 9R silicon polytype by ion implantation

TL;DR: In this article, transmission electron-microscopy examination revealed the appearance of hexagonal silicon inclusions in the subsrface silicon layer upon ion implantation and subsequent heat treatment of the SiO2/Si structure.
Abstract: Transmission electron-microscopy examination revealed the appearance of a hexagonal silicon (9R polytype) inclusions in the subsrface silicon layer upon ion implantation and subsequent heat treatment of the SiO2/Si structure. The formation of this hexagonal phase is stimulated by mechanical stresses arising in the heterophase system in the course of ion implantation.
Citations
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Journal ArticleDOI
TL;DR: This review aims to give a detailed overview of these exciting new properties and routes for the synthesis of novel Si allotropes, and the key problems and the developmental trends are put forward.
Abstract: Diamond cubic silicon is widely used for electronic applications, integrated circuits, and photovoltaics, due to its high abundance, nontoxicity, and outstanding physicochemical properties. However, it is a semiconductor with an indirect band gap, depriving its further development. Fortunately, other polymorphs of silicon have been discovered successfully, and new functional allotropes are continuing to emerge, some of which are even stable in ambient conditions and could form the basis for the next revolution in electronics, stored energy, and optoelectronics. Such structures can lead to some excellent features, including a wide range of direct or quasi-direct band gaps allowed efficient for photoelectric conversion (examples include Si-III and Si-IV), as well as a smaller volume expansion as lithium-battery anode material (such as Si24, Si46, and Si136). This review aims to give a detailed overview of these exciting new properties and routes for the synthesis of novel Si allotropes. Lastly, the key problems and the developmental trends are put forward at the end of this article.

17 citations


Cites background from "Formation of hexagonal 9R silicon p..."

  • ...Subsequently, many other metal ions such as Kr+ and Ga+ have been implanted into silicon or silica/silicon substrate to explore the mechanism and discover more new phenomena [81,82]....

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Journal ArticleDOI
TL;DR: In this paper, the formation of a 9R phase in a cubic silicon substrate near the interface with silicon dioxide under irradiation with Kr+ ions (80 keV) and subsequent annealing at 800 °C is demonstrated.
Abstract: Light-emitting layers of hexagonal 9R silicon were synthesized by ion implantation into SiO2/Si substrates. Using cross-sectional transmission electron microscopy, the formation of a 9R phase in a cubic silicon substrate near the interface with silicon dioxide under irradiation with Kr+ ions (80 keV) and subsequent annealing at 800 °C is demonstrated. Arguments explaining how the new phase is formed through hexagonalization of the initial cubic silicon are presented. The synthesized 9R-Si layers are characterized by a low-temperature photoluminescence line with the maximum at a wavelength around 1240 nm. First-principles calculations of the 9R-Si electronic band structure showed that this material is an indirect-gap semiconductor with the bandgap value of 1.06 eV, which is in good agreement with the spectral position of the experimentally observed photoluminescence line. Believing that the proposed approach can be extended to other semiconductors, we calculated the electronic band structure of 9R germanium and predicted that the hexagonalization converts cubic Ge into a direct-gap semiconductor with the bandgap of 0.48 eV.Light-emitting layers of hexagonal 9R silicon were synthesized by ion implantation into SiO2/Si substrates. Using cross-sectional transmission electron microscopy, the formation of a 9R phase in a cubic silicon substrate near the interface with silicon dioxide under irradiation with Kr+ ions (80 keV) and subsequent annealing at 800 °C is demonstrated. Arguments explaining how the new phase is formed through hexagonalization of the initial cubic silicon are presented. The synthesized 9R-Si layers are characterized by a low-temperature photoluminescence line with the maximum at a wavelength around 1240 nm. First-principles calculations of the 9R-Si electronic band structure showed that this material is an indirect-gap semiconductor with the bandgap value of 1.06 eV, which is in good agreement with the spectral position of the experimentally observed photoluminescence line. Believing that the proposed approach can be extended to other semiconductors, we calculated the electronic band structure of 9R germaniu...

15 citations

Journal ArticleDOI
TL;DR: In this paper, the luminescent properties of SiO2/Si structures irradiated with Kr+ ions at different doses and annealed at 800 °C have been systematically investigated.
Abstract: The study of hexagonal silicon polytypes attracts special attention due to their unique physical properties compared to the traditional cubic phase of Si. Thus, for some hexagonal phases, a significant improvement in the emission properties has been demonstrated. In this work, the luminescent properties of SiO2/Si structures irradiated with Kr+ ions at different doses and annealed at 800 °C have been systematically investigated. For such structures, a photoluminescence line at ∼ 1240 nm is observed and associated with the formation of hexagonal 9R-Si phase inclusions. It is found that the variation in the thickness of oxide film and the relative position of ion distribution profile and film/substrate interface leads to a regular change in the luminescence intensity. The nature of the observed dependencies is discussed as related mainly to the interplay between the factors contributing to the formation of 9R-Si inclusions and the generation of radiation defects in the Si substrate—centers of nonradiative recombination. The revealed regularities suggest optimal ion irradiation conditions for synthesis of optically active 9R-Si phase in diamond-like silicon.

6 citations

Journal ArticleDOI
TL;DR: In this paper, the luminescence properties of SiO2/Si structures irradiated with Kr+ ions at different doses and annealed at 800°C have been systematically investigated.
Abstract: The study of hexagonal silicon polytypes attracts special attention due to their unique physical properties compared to the traditional cubic phase of Si. Thus, for some hexagonal phases, a significant improvement in the emission properties has been demonstrated. In this work, the luminescent properties of SiO2/Si structures irradiated with Kr+ ions at different doses and annealed at 800 {\deg}C have been systematically investigated. For such structures, a photoluminescence line at ~ 1240 nm is observed and associated with the formation of hexagonal 9R-Si phase inclusions. It is found that the variation in the thickness of oxide film and the relative position of ion distribution profile and film / substrate interface leads to a regular change in the luminescence intensity. The nature of the observed dependencies is discussed as related to the interplay between the desirable 3C-Si -> 9R-Si structural transition and generation of nonradiative defects. The revealed regularities suggest optimal ion irradiation conditions for synthesis of optically active 9R-Si phase in diamond-like silicon.

4 citations

Journal ArticleDOI
Yalan Wei, Jiaxin Li, Xizhi Shi, Jin Li, Chaoyu He 
TL;DR: In this article , the authors proposed five new allotropes (5H, 6H-2, 7H-1, 7 H-2 and 7 H -3) with similar stacking manners to Si-I but in different orders by random sampling strategy combined with group and graph theory.

3 citations

References
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Journal ArticleDOI
TL;DR: SRIM as discussed by the authors is a software package concerning the stopping of ion/atom collisions, and individual interatomic potentials have been included for all ion and atom collisions in the SRIM package.
Abstract: SRIM is a software package concerning the S topping and R ange of I ons in M atter. Since its introduction in 1985, major upgrades are made about every six years. Currently, more than 700 scientific citations are made to SRIM every year. For SRIM-2010 , the following major improvements have been made: (1) About 2800 new experimental stopping powers were added to the database, increasing it to over 28,000 stopping values. (2) Improved corrections were made for the stopping of ions in compounds. (3) New heavy ion stopping calculations have led to significant improvements on SRIM stopping accuracy. (4) A self-contained SRIM module has been included to allow SRIM stopping and range values to be controlled and read by other software applications. (5) Individual interatomic potentials have been included for all ion/atom collisions, and these potentials are now included in the SRIM package. A full catalog of stopping power plots can be downloaded at www.SRIM.org . Over 500 plots show the accuracy of the stopping and ranges produced by SRIM along with 27,000 experimental data points. References to the citations which reported the experimental data are included.

6,906 citations

Journal ArticleDOI
25 Jan 1963-Science

301 citations

Journal ArticleDOI
TL;DR: In this article, an ab initio calculation of hexagonal polytypes of C, Si, and Ge in equilibrium and under hydrostatic pressure was performed. And the results were interpreted within the axial next-nearest-neighbor Ising model.
Abstract: Results of ab initio calculations are reported for hexagonal polytypes of C, Si, and Ge in equilibrium and under hydrostatic pressure. For each polytype $2H,$ $3C,$ $4H,$ and $6H,$ the atomic geometry, the energetics, and the electronic structure are studied. The resulting lattice parameters are in good agreement with measured values. While $3C$ is the most stable polytype for each element, pressure-induced phase transitions to hexagonal modifications are found to be possible. Silicon is the most favorable candidate in this respect. The results are interpreted within the axial next-nearest-neighbor Ising model. It simultaneously allows the derivation of formation energies for stacking faults in agreement with other calculations and measurements. We predict significant differences in the band structures between the hexagonal polytypes and the diamond structure. This holds especially for the energy gaps and the location of the conduction-band minima. Trends with the hexagonality of the polytype and the element are derived.

132 citations

Journal ArticleDOI
Teh Y. Tan1, Helmut Föll1, S. M. Hu1
TL;DR: In this paper, a phase transformation scheme was proposed for the silicon dc to hexagonal transformation, which was argued that the transformation may be induced by a uniaxial compressive stress and therefore represents a stressrelief mechanism.
Abstract: An analysis of electron diffraction data from silicon wafers implanted with 80 keV As+ at high dose rates has shown the presence of a hexagonal phase of Si (a one-element wurtzite structure). The hexagonal silicon consists of small rod-like particles with an orientation relationship to the diamond-cubic (d.c.) silicon lattice given approximately by 〈0001〉hex | 〈110〉d.c. and 〈0110〉hex | 〈001〉d.c.. This hexagonal silicon may also be produced by indenting the wafer surfaces at about 500 to 600°C (Eremenko and Nikitenko 1972) which produces large platelets with {115}d.c. habit planes. A phase transformation scheme is proposed for the silicon dc to hexagonal transformation. It is argued that the transformation may be induced by a uniaxial compressive stress and therefore represents a stress-relief mechanism. A structure model of the dc-hexagonal interface is proposed which consists of five- to seven-membered atomic rings without dangling bonds.

98 citations